Digital Predistortion Linearization of a GaN HEMT Push-Pull Power Amplifier for Cable Applications With High Fractional Bandwidth

This paper presents two linearization strategies for a custom-designed wideband push-pull (PP) power amplifier (PA) for wired communication applications such as, for example, cable TV. Two digital predistortion (DPD) behavioral models are proposed to meet the in-band and out-of-band linearity requirements when efficiently amplifying wideband DOCSIS signals with high fractional bandwidth (FBW). A radiofrequency (RF) DPD linearizer based on a band-pass generalized memory polynomial (BP-GMP) behavioral model and a baseband (BB) I-Q DPD linearizer based on a harmonic distortion GMP (HD-GMP) behavioral model are proposed. Both DPD models take into account the harmonic distortion typical of high FBW amplification. Experimental results will show high efficient and linear amplification of a $4\times192$ MHz composite DOCSIS signal by properly combining a crest factor reduction (CFR) technique and the proposed DPD strategies.

I. Introduction

In both wireless and wired environments the need for transmitting signals over long distances makes the power amplifier (PA) one of the key elements in the transmitter side. Not only because it is the main responsible for introducing nonlinear distortion but also because its power consumption is relevant enough to significantly impact capital expenditures (CAPEX) and operational expenditures (OPEX).